Abstract: A method and apparatus allows a data tuner to communicate information. An identifier of the frequency used to transmit the data may be transmitted by a control center to a receiver coupled to the data tuner to notify a user to tune to that frequency to receive the data. The data tuner may transmit a frequency identifier to the control center to instruct the control center which frequency to use to broadcast the data. This frequency may be the frequency to which a user is already tuned, or a frequency meeting certain criteria, such as one having reception exceeding a threshold amount. The data tuner may scan header information provided by several frequencies to identify a frequency meeting certain criteria. The data tuner may provide information to a control center using a transmitter coupled to the data tuner in response to requests for information received by the data tuner.

Abstract: A broadcast transmitting and receiving system includes a receiver having multiple tuners. A data tuner receives a data stream indicating the type of programming being broadcast by one or more stations. Based on information in the data stream, the frequency of operation of a sound tuner is adjusted to provide the user with a desired type of programming. Various modes of operation are provided, some employing a user interface and others being operable without user intervention.

Abstract: A system for transmitting a main channel signal, a first subcarrier signal, and a second subcarrier signal includes a control signal generator for producing a control signal in response to the amplitude of the main channel signal and the first subcarrier signal, a modulator coupled to the control signal generator and generating the second subcarrier signal, a voltage controlled amplifier for providing the second subcarrier signal at an injection level that varies with the control signal, and a transmitter for transmitting the second subcarrier signal at the varying injection level.